1. Field of the Invention
The present invention relates to a light controlling apparatus and an optical system which are used in a small-size image pickup equipment.
2. Description of the Related Art
Various types of light controlling apparatuses have hitherto been used. As one of the types thereof, a plug-in type light controlling apparatus in which, a single or a plurality of incident-light controlling means is displaced mutually inside and outside an optical path by an electromagnetic driving source, and optical characteristics of incident light which passes through the optical path is changed, is available. In recent years, with an achievement of high-quality image of a portable equipment having an image pickup function and a small-size image pickup equipment such as a micro video scope, with regard to optical elements such as a lens, an aperture, and an optical filter, there has been increasing demand for an application of a focusing lens, a variable aperture, and a variable special characteristic filter instead of a conventional fixed focusing lens, a fixed aperture stop, and a fixed special characteristic filter.
As the abovementioned plug-in type light controlling apparatus has a simple structure, it has been gathering attention as a light controlling apparatus which is suitable for small sizing, which in turn, is suitable for such small-size image pickup equipment.
An example of such plug-in type light controlling apparatus suitable for small-sizing has been disclosed in Japanese Patent Application Laid-open Publication No. Hei 10-20360, in which, a diaphragm plate is fixed to a rotor which is polarized to bipolarity, via a shaft, and the rotor is inserted through a rotating hole into a coil which has been formed to be ring-shaped, and is fixed to be freely rotatable by a shaft attachment which is formed in an upper cover and a lower cover.
However, in a structure disclosed in Japanese Patent Application Laid-open Publication No. Hei 10-20360, an area in which the coil can be formed is limited to be more than a diameter of an opening formed in the upper cover and the lower cover, and within an outer peripheral diameter of the upper cover and the lower cover.
For reducing further a diameter of the light controlling apparatus, it is necessary to shorten a coil-length or to reduce the number of turns of the coil together with the contraction of the area in which the coil can be formed. This leads to a degradation of magnetic field generated in the coil, thereby leading to a degradation of a rotating torque of the diaphragm plate, which hinders a stable drive.
Moreover, in reducing further the diameter of the light controlling apparatus, not only that the area in which the coil can be formed is reduced but also there may arise a problem that there is no space to provide the coil in first place.